A wind turbine transfers the energy of moving air into electrical energy. The moving air accelerates the rotor of the wind turbine. The rotation of the rotor is transferred to an electrical generator. The electrical generator transforms the rotational energy into electrical energy. In the last years the concept of a direct driven wind turbine was established. In a direct driven wind turbine, the rotational energy of the rotor is transferred to the generator directly without the use of a gearbox. In a direct driven wind turbine the rotor of the wind turbine is directly connected to the rotor of the electrical generator. The chain of mechanically connected parts leading from the rotor of the wind turbine to the rotor of the generator is called the drive train of the wind turbine.
To allow the rotational movement and to provide the necessary stability of the rotating parts, the drive train is mounted with at least one bearing. This bearing allows the drive to train to rotate. At the same time, it provides the necessary stability by supporting the radial and axial loads and the bending moments present in the drive train. WO 2011/003482 A2 describes a wind turbine main bearing realized to bear a shaft of a wind turbine. The bearing comprises a fluid bearing with a plurality of bearing pads. The document describes a bearing with a cylindrical bearing surface and a series of trust pads.
The plain bearing has to provide a large surface to withstand the forces present in the drive train. As a consequence, the pads used for the cylindrical bearing surface are very large, heavy and difficult to exchange.